The next step would have been to ask you to issue this command:
inxi -CGxxz
but since you have no display, this won't work anyway.
The advice that @jymm gave you was spot on.
The linked article, however, contains an error.
It is not the ESC key but the SHIFT key that you need to hold during boot.
So, boot your PC while holding the shift key.
If you see that again, that means you are either too early or too late with holding the shift key.
Try hammering the key instead of holding it until a menu like this appears:
Choose Advanced options for ubuntu
You will see probably 4 entries, the one with the '*' in front is the kernel that will be booted by default.
Choose the other one (not the ones marked as rescue mode).
If you can boot now, you can start with keeping this menu visible at any boot for the time being. Follow the steps that @ricmarques showed in the post above.
Now issue the earlier mentioned command.
inxi -CGxxz
And post the output here.